Seismic Behavior of Steel Frames with Geopolymer and Conventional Mortars Under Rigid and Flexible Joint Conditions

This work experimentally examines the seismic performance of steel frames with masonryinfill walls produced with geopolymer and traditional mortars under both rigid and flexiblejoint configurations. Four single-span specimens were evaluated on a uniaxial shake tableutilizing eleven scaled earthquake records that represent both in-plane and out-of-planeexcitations. Flexible joints markedly diminished acceleration requirements and enhanceddeformation capacity in comparison to stiff systems. Rigid frames attained maximumaccelerations of 1.82 ± 0.21 g, whilst flexible-joint specimens measured 1.15 ± 0.18 g; theassociated lateral displacements were 6.8 ± 0.9 mm and 10.5 ± 1.1 mm, respectively.Geopolymer mortar improved interface adhesion and rigidity, elevating dominant frequencies in rigid systems by around 40% and fostering more ductile behavior in flexiblestructures. Frequency-domain analysis indicated that decreases in dominant frequencycorrelated with stiffness deterioration. Geopolymer–flexible systems yielded the minimal acceleration responses and displayed only negligible cracking, indicating enhancedseismic performance.